105 
inch columbiad, fired with ten and a quarter pounds of 
powder from the distance of two hundred yards. The plate 
of iron will be deeply indented at the point of impact, the 
ball carving for itself a smooth bed of the shape and size of 
one hemisphere, in which it will be found broken into many 
pieces easily separable, and it will besides be somewhat bent 
generally. The masonry behind will be much jarred, and, 
unless strongly bonded, be considerably displaced ; moreover, 
unless the thickness of three feet is well tied into thicker 
masses immediately adjacent on the sides and above and 
below, the general damage will be severe. 2 
“Second, This plate will be much the stronger for being 
in a single mass, and not made up of several thinner plates. 
The continuity effected by bolts and rivets of the made-up 
plates is broken even by weak assaults, so that afterwards 
the stronger, instead of a joint opposition, finds only a suc- 
cession of feeble resistances. 
“Third, A thickness of two inches is ample for shutters 
designated to stop the largest grape-shot. With this thick- 
ness they will be neither perforated nor deformed by any- 
thing less than cannon-balls or shells. These shutters also, 
for the reason just given, should be made of a single thick- 
ness. The firings show the necessity of concealing entirely, 
even from the smallest iron missile, their hinges and fasten- 
ings, : 
“Fourth,A wrought-iron plate of half an inch in thick- 
hess is adequate to protect the outer margins and the offsets 
of embrasures from injury by grape or canister shot.” 
These facts established, the effect of the form and dimen- 
sions of the embrasures in carrying in the smaller missiles 
Was investigated; the recorded results will enable us to 
appreciate the force of Montalembert’s expression, “ mur- 
derous funnels,” as even its author could not do. 
. 
